Questions and Answers

Here are some of the typical questions we get on kitchen range hoods and kitchen ventilation in general:
Q.
How often should i clean my filters
 
A.
We always recomend weekly or at least every two weeks. Why so often - well the purpose of the range hood filters is to collect the grease and solid contaminents in the vapor from the cook top. It therefore makes sense that regular cleaning will stop these contaminents from congealing on the filters. Most filters are dishwasher safe. Another tip is to ensure that the filters are "dried off" before re-installing them otherwise water will drip down onto the cooking surface or worse still if the fan is powered up before they are dry it could suck water up into the motor.
 
Q.
How wide should the hood fan or range hood be
 
A.
Ideally the hood should be 6" wider for a wall mount hood. For an island mount hood it is advisable to make the island deeper than the cook top as well - say 27" instead of 24". Earlier we discussed how vapor expands as it rises - thats why we recomend wider. Islands in particular are exposed to cross drafts and this further contributes to the challenge of capturing all those rising vapors.
 
Q.
Are baffle filters better than mesh filters
 
A.
In our opinion yes. Baffle filters are more effective, because of their unique design at capturing the smoke and steam than mesh filters and they are generally quieter than mesh filters. Quieter is really only an issue with high powered fans where we always try to minimize the noise of airflow. They are also more expensive!!!
 
Q.
Why do you need a range hood
 
A.
Cooking creates vapor that is laden with grease, moisture and of course some pretty powerful odors. Without an effective range hood those odors and grease laden vapor will drift through the home and attach to fabrics and surfaces. Allied to this is our homes have become extremely air tight - we dont have our windows and doors open anymore because of the AC or heating system - so all of these bad vapors get absorbed into the fabric, carpeting and onto the solid surfaces.
 
Q.
How Powerful should the exhaust blower be for my range hood?

A.
Typically the manufacturer of the cooking appliance specifies how powerful and how high the range hood should be above the stove. In the absence of this information call the stove supplier or you can use the industry rule of thumb as a guideline - 1cfm of range hood power for every 100btu of cook top output. This formula takes the maximum btu output of the cooktop - assuming the worst case scenario that all burners (gas) are on at the same time. So for example a 60 000btu gas stove top would need about 600cfm. Electric or induction cook tops are a little different - the rule of thumb here is 100cfm for every 10" of cook top - so a 30" electric cook top would need say 300cfm minimum. There are of course other factors involved not the least of which is the ducting. At Custom Range Hoods we offer hoods in 400cfm, 600cfm, 1000cfm and 1400cfm or multiples of these - yes sometimes 1400cfm is not enough - we recently completed a project with a 10' wide hood and 2400cfm external blowers.

Q.
How big should the ductwork be for the range hood

A.
Firstly one should size the duct as a minimum for the cfm that the blower is exhausting. Secondly one must factor in how many bends and how long is the duct run - it makes sense that a 200ft duct run of 6" will be less effective than a 20ft duct run of 6". Bends in ductwork seriously degrade the efficiency of the duct run - for example rather use two 45 degree bends slightly spaced than one 90 degree bend. Finally factor in whether an internal or external blower system is being used - external blowers are more efficient than internal blowers by about 20% - its easier to pull the heavy vapor laden air through the duct than to push it. Now there is as far as we know no scientific formulas or wizadry involved here. So you are now totally confused right - the answer is always oversize the ducting when in doubt - thats all we do - 600cfm = minimum 6" duct ideally 8"; 1000cfm = minimum 8" and 10" would be nice, over 1000cfm minimum 10" duct - or equivalents in rectangular ducting. If you have a really bad duct run and no other way to do it - go with and external blower.

Q.
How high should the range hood be above the cook top?

A.
The hood manufacturers specify this distance in their installation instructions.Code in most provinces or states specify a minimum of 30" distance to a combustible surface - we always advice our clients to set the hood at a minimum of 30" = if the filters get laden with grease because the filters haven't been cleaned for a year - that in our opinion constitutes a combustible surface. No jokes aside - 30" minimum is a convenient height and 34" maximum. Of interest to consider that for every 30" that vapor rises it expands outwards 3" - so if the hood is set at 60", which is totally ineffective, the vapors would have expanded outwards at least 6" in all directions - so the hood would in this case have to be 12" wider than the cooktop